Ravens coach John Harbaugh can go in many different directions when choosing his fourth offensive coordinator in as many seasons. Let's sort out some potential candidates:

Hot name

Adam Gase, ex-Broncos offensive coordinator: He is the early front-runner because of his success. The Broncos scored an NFL-best 1,088 points (34 points per game) in his two years of calling the plays. Some will question how much control Gase had when quarterback Peyton Manning is signaling audibles at the line. Gase, 36, has drawn interest as a head coach, interviewing with four teams (he nearly got the San Francisco 49ers job). His strength is adapting the offense to his players. He helped reconfigure the Broncos' offense to a read-option one for Tim Tebow in 2011, then retooled it for Manning a year later. It doesn't hurt that Gase worked with Nick Saban, who has a good relationship with Ravens general manager Ozzie Newsome, and also crossed paths with Ravens defensive coordinator Dean Pees. The hiring of Gase could benefit the Ravens in free agency if they have their sights on a couple of Broncos playmakers -- wide receiver Demaryius Thomas and tight end Julius Thomas. The Chicago Bears are also interested in Gase to be their offensive coordinator.

Most experienced options

Marc Trestman, ex-Chicago Bears head coach: Nicknamed the "quarterback whisperer" for his success at developing passers, Trestman has been an offensive coordinator for four NFL teams: the Cleveland Browns, San Francisco 49ers, Arizona Cardinals, and Oakland Raiders. Though it didn't work out with Jay Cutler, Trestman helped the Bears become the NFL's second-highest scoring team in 2013 with Josh McCown at quarterback. Trestman, 59, is known for his wide-open offenses with a lot of shotgun formations. He will get a strong recommendation from Jim Harbaugh, who said Trestman "taught me everything" when they were with the Oakland Raiders' staff 12 years ago. Trestman had been touted as the leading offensive coordinator candidate in Oakland, but it looks like the Raiders are now leaning toward Philadelphia Eagles quarterbacks coach Bill Musgrave.

Greg Knapp, Broncos quarterbacks coach: He has had five stints as an offensive coordinator: the 49ers, Atlanta Falcons, Raiders (twice) and Seattle Seahawks. Knapp, 51, did serve two years as the quarterbacks coach for the Houston Texans (2010-11), so he is familiar with Kubiak's style of offense. He's also committed to running the ball, which is a big emphasis with John Harbaugh. In his three seasons with the Falcons (2004-06), Atlanta led the NFL in rushing, although a large chunk came from the scrambling of quarterback Michael Vick. There is a chance Knapp will remain with the Broncos because of his history with Kubiak.

Thoose with ties to John Harbaugh

Marty Mornhinweg, ex-New York Jets offensive coordinator: He spent five seasons with Harbaugh on the Eagles' staff (2003-07). It didn't end well for Mornhinweg in New York, where there was reported friction with Rex Ryan and the Jets finished 28th in scoring (17.7). Before the struggles in New York, he built an impressive resume with the Eagles, who finished in the top 10 in total offense in five of his seven seasons as the primary play-caller. Mornhinweg, 52, was also offensive coordinator for the San Francisco 49ers and the head coach for the Detroit Lions. Even if Harbaugh doesn't hire Mornhinweg to be coordinator, it wouldn't be surprising if he joined the coaching staff.

Jim Hostler, ex-Buffalo Bills senior offensive assistant: He was a finalist for the Ravens' offensive coordinator job last offseason before Kubiak entered the picture late. Hostler, 49, then left the Ravens after six years of being their wide receivers coach to join the Bills. He spent one season as a coordinator in the NFL, calling the plays for the 49ers in 2007. The Ravens might not consider Hostler because it would look like a step backward, going with the runner-up to Kubiak a year later. But Hostler has a good reputation in the Ravens' building.